Windshield wiper arms used on motor vehicles usually comprise a fixing part or mounting head, a joining piece or retainer, an arm rod and a pressure spring. The mounting head is typically manufactured from die cast zinc or aluminum. The retainer is typically formed out of sheet metal in a generally U-shaped configuration. The arm rod is rigidly carried with the retainer and is pivotally attached to a wiper blade assembly. The mounting head is unrotatably coupled to the drive shaft of the host wiper drive which is arranged below the windshield of the automotive vehicle and is isolated by means of a known mechanism. To enable lifting of the wiper from the windshield, the retainer is pivoted to the mounting head about a mounting axis, which extends roughly perpendicular to the wiper drive shaft. A tension spring is typically employed for urging the wiper blade firmly against the windshield.
In order to ensure the proper contact pressure of the wiper at the windshield and its correct alignment in relation to the windshield surface, the wiper holder must be aligned in relation to the windshield surface, which may be different in various vehicle designs. Ideally, the wiper blade should be maintained perpendicular to the windshield surface.
Normally, windshield cleaning systems of modern motor vehicles comprise a wiper system as well as a windshield washing system including a washing liquid reservoir and a pump by which washing fluid is sprayed onto the windshield to be cleaned via a spraying device. There are motor vehicles in which this spraying device is stationarily arranged on the engine compartment hood. In other windshield cleaning systems the spraying device is fixed on the wiper arm. The advantage of this latter system is that the washing liquid is sprayed immediately in front of the wiper blade.
Mounting of wiper fluid spray nozzles on the wiper arm assembly has proven to be problematic inasmuch as modern vehicle windshields tend to be increasingly non-planar, requiring the wiper arm and blade assembly to flex to effectively apply constant wiping pressure over the entire swept surface.
A problem often encountered with hood mounted washer jets is that the cleaning fluid will be delivered to the windshield at a location above the wiper blade which is already partly through its upward cycle or at a point below the wiper blade when it is partly through its downward path, such that the cleaning fluid is spread by the wiper blade over only a portion of the windshield, thus resulting in only partial cleaning thereof. This problem generally requires the operator to repetitively supply fluid in order to clean the entire windshield, which wastefully depletes the fluid in the reservoir.
A similar problem encountered with hood-mounted washer jets is that delivery of the fluid onto the windshield may be to an area behind the path of the windshield wiper travel which may obstruct clear vision through the windshield until another half-cycle of the wiper action is completed, and then only a portion of the windshield may be cleaned. A further disadvantage of windshield washer jets of the hood-mounted type is that because the jet outlets are located relatively far from the windshield, if they are not aimed properly or later become misalligned, do to damage to the hood, for instance, the stream of fluid may strike the windshield in an ineffective location or miss the windshield entirely if, in addition, a too strong or to weak pumping action is used. Further, because the washer jets are spaced a relatively long distance from the windshield, a strong pumping force or small washer jet outlet, which may easily become clogged, may be required.
Arm-mounted washer jets are known, but due to high part count, cost of production, difficulty of mounting, or lack of proper fluid distribution, they are not as cost effective in some applications as they otherwise could be.
Although "wet arm" wipers have become more popular recently, they have proven to be either difficult to manufacture and/or expensive, requiring numerous components and complex manufacturing steps and can be difficult to ensure that the spray jets are precisely located on the wiper arm. By way of example, a washer jet described in U.S. Pat. No. 3,827,101 to Wubbe includes a number of components that can be misassembled or loosened in use resulting in leakage of washer fluid and diminished windshield cleaning effectiveness.